Raw SQL when needed in Ruby on Rails - Mini Project: Build & Apply

Raw SQL when needed

📖 Scenario: You are building a simple Rails app to manage a bookstore. You have a books table with columns title, author, and price. Sometimes, you need to run raw SQL queries directly to get specific data quickly.

🎯 Goal: Learn how to write raw SQL queries in Rails using ActiveRecord::Base.connection.execute to fetch data from the books table.

📋 What You'll Learn

Create a hash representing a book with exact keys and values

Create a variable holding a raw SQL query string

Use ActiveRecord::Base.connection.execute with the raw SQL query

Assign the query result to a variable

💡 Why This Matters

🌍 Real World

Sometimes Rails queries need to be very specific or optimized. Writing raw SQL lets you do exactly that when ActiveRecord methods are not enough.

💼 Career

Many Rails jobs require understanding how to run raw SQL safely and effectively for performance or complex queries.

1

Create a book hash

Create a hash called book with these exact key-value pairs: title: 'Eloquent Ruby', author: 'Russ Olsen', and price: 30.

Ruby on Rails

# Create the book hash with title, author, and price
# Your code here

Need a hint?

Use Ruby hash syntax with keys title, author, and price.

2

Write a raw SQL query string

Create a variable called sql_query and assign it the string "SELECT * FROM books WHERE price < 40".

Ruby on Rails

book = { title: 'Eloquent Ruby', author: 'Russ Olsen', price: 30 }
# Create the raw SQL query string in sql_query
# Your code here

Need a hint?

Assign the exact SQL string to sql_query.

3

Execute the raw SQL query

Use ActiveRecord::Base.connection.execute(sql_query) and assign the result to a variable called result.

Ruby on Rails

book = { title: 'Eloquent Ruby', author: 'Russ Olsen', price: 30 }
sql_query = "SELECT * FROM books WHERE price < 40"
# Execute the raw SQL query and assign to result
# Your code here

Need a hint?

Use ActiveRecord::Base.connection.execute with sql_query.

4

Access the first row from the result

Assign the first row of result to a variable called first_book using result.first.

Ruby on Rails

book = { title: 'Eloquent Ruby', author: 'Russ Olsen', price: 30 }
sql_query = "SELECT * FROM books WHERE price < 40"
result = ActiveRecord::Base.connection.execute(sql_query)
# Assign the first row of result to first_book
# Your code here

Need a hint?

Use result.first to get the first row.